The present invention regards a method and a device for controlling semiactive suspensions of motor vehicles.
The design of active suspension systems is aimed, on the one hand, at minimizing the forces acting on the passengers in order to increase comfort (mainly by eliminating the effects of acceleration), and, on the other, at maximizing driving safety and car handling by preventing wheelhop.
In the past, with traditional suspension systems, it was not possible to meet both of these requirements, and it was necessary to choose a compromise between them, favoring the aspects of comfort or safety according to the desired characteristics of the vehicle. To overcome these problems, active suspension systems have been developed, in which the rigidity of the suspensions can be varied by pneumatic pumps driven by respective motors. In these systems, the pump, according to the type of behavior required, modulates the pressure of the air or gas present in the suspensions so as to modify their damping coefficient. In this way, it is possible to improve simultaneously both comfort and safety.
Active suspension systems are, however, very costly and involve high levels of consumption. Consequently, semiactive suspension systems have been developed, in which modulation of the rigidity of the suspensions is obtained by modifying the flow of a liquid (oil) inside the suspension shock-absorbers. In particular, according to one known solution, a control system governs a stepping motor, which gradually opens and closes a valve that has a number of preset positions, for example nine, so as to modify the section through which the oil passes. According to another known solution, the control system acts on the viscosity of the oil, suitably modifying it according to the desired rigidity of the suspensions.
Semiactive suspension systems involve lower costs than do active suspension systems, as well as low energy consumption. Consequently, they are currently preferred.
Present semiactive suspension systems use controllers of the proportional-integrative-derivative (PID) type to regulate opening of the valve, and hence regulate the system.
The disclosed embodiments of the invention provide an improved control system for semiactive suspensions that may be easily adapted to the needs and demands of users (vehicle manufacturers) and may respond rapidly to the specific driving conditions.
According to the present invention, a method and a device for controlling semiactive suspensions of motor vehicles are provided, which include detecting forces acting on a semiactive suspension having an actuator; calculating a subsequent position value of the actuator using fuzzy logic; and controlling the actuator in accordance with the subsequent position valve.